This invention relates to a connection cap for insulating and protecting conductors of a wire from the exterior and for joint-connecting the conductors of the wires together, and also relates to a wire connection method using this connection cap.
As one example of related connection caps of this kind as well as one example of wire connection methods using it, there is known one which has been proposed by the Applicant of the present application, and is shown in FIG. 7 (For example, Patent Literature 1).
This related example provides the connection cap 50 excellent in connecting-operation efficiency and waterproofness, and also provides the wire connection method using it. The connection cap 50 comprises a cap body 51 for the insertion of distal end portions of a plurality of wires 59 thereinto, and an insulative seal layer 56 which is filled in the cap body 51, and penetrates into a gap between conductors 59a and the cap body 51 and also into interstices between sheaths 59b. 
The wires 59 are so-called splice wires each having the conductors 59a exposed by removing the sheath 59b. The conductors 59a are beforehand joined together by any of various methods, such as press-fastening, soldering, welding and thermal press-fastening, before these conductors are inserted into the cap body 51. The cap body 51 is made of an insulative synthetic resin such as polyvinyl chloride, polyethylene or polypropylene, and has such a configuration that a closed back wall 52 is provided at its distal end and that an opening 53 for the insertion of the end portions of the wires 59 therethrough is provided at its rear end.
A holder plate 55 for fixing the wires is formed at the open end of the cap body 51, and projects therefrom in a direction opposite to the direction of insertion of the wires 59. This holder plate 55 serves to prevent the withdrawal of the connection cap 50, and the holder plate 55 is held against the wires 59, and a tape 57 is wound on the wires 59, including the holder plate 55, thereby fixing the connection cap 50.
The seal layer 56 is formed by curing an uncured resin such as an epoxy resin and a polyurethane resin having insulating and waterproof properties. The uncured resin, having the viscosity of 100 to 5000 centipoise (0.1 to 5 Pa·s), is used so that it can penetrate into a gap between the conductors 59a and the cap body 51 and also into the interstices between the sheaths 59a. 
When the wires 59 are to be connected to the connection cap 50, the uncured resin is poured into the connection cap 50, and then the wires 59 are inserted thereinto. As a result, the uncured resin penetrates into the gap between the conductors 59a ad the cap body 51a, the interstices between the sheaths 59b and the interstices between the conductors 59 because of a capillary phenomenon. Then, the connection cap 50 is held at a temperature of 20 to 60° C. for 2 to 30 minutes, so that the uncured resin is cured, and the wires 59 are connected to the connection cap 50.
Patent Literature 1
                JP-A-10-243539 Publication        
However the above related connection cap 50 and the wire connection method, using it, have the following problems to be solved.
Firstly, the process of connecting the wires 59 to the connection cap 50 comprises the joint step of joining the conductors 59a of the wires 59 by press-fastening, welding or the like, the insulating and waterproofing step of inserting the conductors 59 into the cap body 51 filled with the uncured resin (serving as a sealant) and penetrating the uncured resin into the interstices between the conductors 59a of the wires 59, the curing treatment step of curing the uncured resin under the predetermined conditions, and the tap winding step of winding the tape 57 on the wires 59, including the holder plate 55. The wire-connecting operation was carried out via many steps, and therefore there were encountered problems that much time was required and that the cost was high.
And besides, there was a fear that when the conductors 59a were merely immersed in the uncured resin, the uncured resin could not completely penetrate into the gap between the conductors 59a and the cap body 51, the interstices between the sheaths 59b and the interstices between the conductors 59a. When the viscosity of the uncured resin was lowered so that it could completely penetrate, there was a fear that the uncured resin leaked out of the opening 53 of the connection cap 50.
Furthermore, when the gap between the wires 59, inserted in the connection cap 50, and the connection cap 50 was large, it took much time for the uncured resin to be cured, and a yield decrease is encountered in the curing treatment step, and besides there was a fear that after the curing of the resin, the wires 59 within the connection cap 50 were moved by an accidental external force, so that cracks or the like developed in the seal layer 56, thus adversely affecting the waterproof ability, and water or the like intruded into the connection cap 50.